In light of the increasing costs of labor, attempts are continuously being made to develop apparatuses, tools, and other articles for the construction trade to increase the efficiency of the construction work being performed and to maintain control of the increasing cost of labor. One particular area in which such attempts have been directed is the preparation and installation of large, heavy rectangular objects, such as windows, panels and doors. These attempts are more particularly being directed in the area of construction of public or commercial buildings as there is an increasing practice to use heavier and larger windows, panels, and doors in construction of this type.
In the preparation and installation of such objects, it is often necessary that the object be arranged in a horizontal position so that object may be prepared for installation. In "hanging" a door, for example, the long edge of the door must be mortised for the hinges prior to installation. The selected door must be thereafter pivoted, however, to a vertical position to size and align the door in the selected door frame.
In conventional construction practices of installing or hanging a door, a workman must first remove the selected door from a stack of doors (which is the standard method of storage for doors at a construction site). The selected door is then carried by the workman to a location where the varied operations of sizing the door, butt routing and mortising the door for hinges, locks and handles are accomplished, all of which require manual manipulation of the door. Once these tasks are completed, the door must then be manually lifted and fitted into the selected door frame. As the weight and size of construction articles of this type have been steadily increasing, this task has naturally become increasingly more difficult for a single workman to perform. For example, it has become nearly impossible for a single workman of average strength to prepare and install a fire door or hospital door, many of which may weigh upwards of two hundred pounds or more. These problems are similarly encountered in the preparation and installation of large, heavy windows or panels. This trend in commercial construction practices has required the use of two workmen to prepare and install such heavy articles, or resulted in a lessening of the number of such objects installed during a work period by a single workman.
There has developed a definite need for an apparatus which permits a single workman to secure, transport and install a heavy object such as a door, window or panel, in a quick and efficient manner.
Prior attempts at providing an apparatus to be used in the practice of securing, transporting, lifting and installing heavy construction articles such as doors, panels, windows, ad the like are disclosed in U.S. Pat. Nos. 2,503,388; 2,955,632; 3,643,935; 3,861,662; 3,871,054; 3,923,167; 4,050,671; 4,141,192; 4,278,244; 4,746,141; and 4,752,173.